Reasons
by ems57
Summary: Peter Pettigrew and Severus Snape are working together to find the horcrux that will ensure their masters immortality, but they are both hiding a secret.
1. Prologue

Disclaimer: J.K. Rowling owns all the characters in this story; I'm just borrowing them for a bit

AN: This was on my friends page for a while, but I've got my own account now so I'm posting it myself

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"Look... It's not that I don't like you… I... Well…" Lily stared exasperated at the boy standing eagerly in front of her. She couldn't count the number of times he had asked her out, always with the same ending. She remembered when she used to hate him, but now they were in seventh year together he had grown on her slightly. She had even started to count him as one of her friends, but she just didn't want him as a boyfriend.

"Just what? Come on Lils, you've never given me a reason. I hate that I love you so much but you don't even have the decency to tell me why you won't even go on one date with me!" Lily gasped. He loved her? He was looking at her desperately. She realised she was going to have to tell him why. But once she did... well, her secret would be out. She could just make something up, but that wouldn't be fair to him, if he really did love her. Taking a deep breath she summoned up her courage and began "Well, um, it' just" he began to look angry with her. "it's just... look, James.." she carried on weakly. The boy glared at her.

"Oh don't bother! You're never going to love me are you, so just forget about it!" He walked off angrily, leaving Lily standing alone by the lake, shocked at what had just happened.

"Wait! You don't understand!" She shouted willing him to turn round. He didn't.

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	2. Chapter One

Peter Pettigrew was staring out the grimy window of a run down house, watching the rain streaming down the windows. Once this house had been a family home, warm and inviting, however nearly sixteen years of neglect had taken its toll, and Godric's Hollow had become dirty and dilapidated.

He had been waiting there for a week unsuccessfully, growing ever more tired of the damp. At the moment, he was waiting for Snape, who was supposed to be checking up on him, and bringing back news to Voldemort. So far, his futile attempts at surveillance had been greeted with more and more contempt, and Peter was sure that today, after seven days of nothing, he would surely receive some punishment worse than Snape's scornful remarks at his failings.

He tensed when he heard a door open somewhere on the floor below. But his fear turned to disbelieving relief when he heard a girl's voice and realised that all his waiting was finally paying off. He began to hear snippets of conversation between the three teenagers downstairs.

"Harry, I would have thought your parents would have lived in a slightly… cleaner house."

"Don't be silly Ron; of course his parents lived in a cleaner house, but no ones exactly going to drop in to do the house work when the owners have been dead for sixteen years, are they?"

"Oh yeah…"

Peter turned quickly into his rat form and ran down to find them. Staying in the shadows, he began to follow the small party, listening to the conversation. He still couldn't make out much of the conversation; most of it was in whispers. The house had an oppressive feel, almost like a graveyard, which seemed to demand silence. Of course, however bad it was for them, it was a thousand times worse for him, with the memories of what happened last time he was in this house still clear in his mind. Peter was shaken out of his memories when he heard the words he had been waiting to hear.

"…horcruxes. After all, we've already destroyed the diary and ring, there's only Nagini, the locket and something of the other two Hogwarts founders to find"

"Only!"

"You know what I mean. I want to find them by the end of the year; I reckon we can't keep this secret from Voldemort long."

"How do you destroy a horcrux anyway…"

Peter was amazed at what he was hearing. Apparently, it was a summary of how much Harry Potter knew and what he planned to do. The only thing that could have please the Dark Lord more would have been hearing the prophecy itself. He was about to turn round to meet Snape with his news, but something stopped him. He had betrayed James once, could he betray his son? Then he remembered the look of anger on his friends face… _"You're pathetic, you know that? Pathetic!" _He had made his decision years ago. The three teenagers in the hallway didn't notice a rat quietly making its way out the door and down the path until it seemingly disappeared into the rain.

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	3. Chapter Two

"We now know that the order knows about the horcruxes. We also know from our spy that the locket is gone." Lestrange, I'm putting you in charge of finding that locket and bringing the other two remaining two horcruxes back to me." The fourth of course is Nagini, and she's here with me. Malfoy and Snape, you two go with him." Narcissa Malfoy stepped forwards to join her sister, along with Snape Oh, and Wormtail, I suppose. You're not much use around here. I want you to get all three of the horcruxes back here before the order does."

Severus Snape watched Voldemort apparate along with the rest of the death eaters he hadn't singled out for this task. He hated being ordered around by Bellatrix, but he supposed that this was a good thing. Such an important task would be useful to him.

"Severus! Thank you so much for helping my son!" Narcissa had replaced her husband while he was imprisoned in Azkaban, and had quickly risen through the ranks of the death eaters, having already gained a reputation for playing more than a small part in her husband's successes. Snape gave her a quick smile, but remained silent.

"And now you have another chance to prove your loyalty. I'm sorry I doubted you, but I think even you can understand, given the circumstances… Well, I suggest that Severus, you find the locket, Cissy, you get the bracelet, and I will get the cup. When Narcissa and I have found ours, we'll help Snape. Everyone agreed?" Everyone nodded, until Peter piped up "What should I do?"

Bellatrix looked up, having forgotten Peter was with them. "Oh, well…" Snape started at the small man with contempt. He despised him, yet he also felt a strange affinity towards him. After all, he was the only one who might share his cause… He would be an unlikely ally, but a possible ally nonetheless. "He can come with me." Bellatrix looked taken aback, but wasn't about to complain about this solution.

"That's that then. Everyone know what you're doing?" There were mummers of assent. "Right then. Meet back here in a week and give a report of how far we've come." She apparated away and her sister quickly followed suite, leaving Severus and Peter alone to find some sort of plan.

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	4. Chapter Three

Peter stared in shock at Snape. Why did he want to find the locket with him? Peter could only think of one reason, and it filled him with dread. Snape, the only death eater who knew why he had joined, must suspect him of not being truly loyal. Well, he would have to prove him wrong then. He couldn't go back to the order or even back to normal society without getting arrested. If he wasn't part of the death eaters then he had nothing. This situation seemed depressing from whatever way he looked at it. He almost wished he could just go back to the order, when he had known what he was fighting for. Almost. But then he remembered why he had joined Voldemort in the first place and anger flared up inside him again. His thoughts were interrupted by an insult from Snape.

"This would be easier, of course, if you had stayed a little longer to find out if they knew where the locket was."

"They said they needed to find the locket! And what was I supposed to do, wait for you to turn up? That's a slight indication that they're being watched, isn't it?" Peter retorted sourly. Snape gave him an impatient look.

"What we need to do is come up with a list of places the locket could be-"

"_If _it hasn't been destroyed already"

"-and check them all. And you'd better hope it hasn't been destroyed. It's worth considerably more to the Dark Lord than your life is, Wormtail."

"And more than yours, I'll bet." Snape just smiled, and Peter had the disconcerting impression that he Snape was confident Voldemort had a reason to keep him alive, meaning most of the blame for a failed mission would be passed onto Peter. Deciding it would benefit him to get down to the task at hand, began a list of where the locket would be.

"Well, I think it was one of Voldemort's enemies who took it."

"So that narrows it down to nearly every wizard. Assuming that it wasn't a jealous death eater who wanted to overthrow their master and gain a bit more power."

"Oh… right."

"However, I feel that it would be more sensible to think first about Voldemorts more powerful enemies. I am almost certain they would be in the order. My immediate guess would be Dumbledore. Now, where would he have hidden it?" Snape mused.

Peter thought for a second before venturing "Hogwarts? That's where he hid the Philosophers stone after all…"

"Yes, we could try there after some other place. I think it more likely that he hid it somewhere that wouldn't endanger his students, or where inquisitive students wouldn't look. The only motive I could imagine him having for not destroying it immediately would be to gain some sort of bargaining power over Voldemort."

"Grimauld Place then"

"We'd better hurry then. It will not remain unguarded long after Dumbledore's death, if indeed there is not already a new secret keeper." Snape said grimly.

"When do you plan we go then?"

"What do you mean? We're going now, Peter!" He replied impatiently, apparating with a pop to London before he had barely finished speaker. Slightly surprised, Peter followed and arrived by Snape's side in the dark square. Disappointed, he saw that there was no house appearing, even when he tried thinking, and in desperation repeating out loud, twelve Grimauld Place… twelve Grimauld Place…

He stared dispiritedly at the spot the house should have emerged.

"No, no luck." said Snape. "Well, we'd better try Hogwarts then."

"Really?" Peter was surprised at Snape taking his suggestion.

"Yes, I can't think of another place Dumbledore would hide it. He mistrusted the ministry, he knew Gringotts wasn't safe. Of course, he knew of other hiding places but he wouldn't have trusted something this valuable into the care of another… I think Hogwarts will be our best bet, for now at least."

Astonished that he had taken his suggestion, and hoping that they were apparating for the last time, Peter followed his companion to the just outside of Hogsmeade, ready to find the locket that would ensure Voldemort's immortality.


	5. Chapter Four

Snape strode up to the castle gates after having cast a disillusionment charm on himself and Peter. The last time he had passed through those doors he had been running to get away from the Order. The memory still haunted him. He hated helping Voldemort in any way, but he couldn't let that show. He couldn't believe he had been about to tell Pettigrew what his aims were… _"Assuming that it wasn't a jealous death eater who wanted to overthrow their master and gain a bit more power"… _How could he have been so careless as to nearly give away his secret without being sure of where Peter's loyalties lay?

"How are we going to get in?" the little voice at his side piped up. He had been wondering that himself, but he wasn't about to tell Pettigrew that. He was toying with the idea of getting Pettigrew to go in in his rat form, but he thought that Dumbledore would have put up defences after Black had managed to get a few years ago. He thought about sending him anyway, after all Pettigrew was getting on his nerves. Suddenly he remembered something about the defences around Hogwarts.

The previous year, the magical enchantments around the castle had been strong, but then so was Voldemort. Dumbledore had been casting the spells around it every month to make sure there wouldn't be any way of the protection being broken. However, his frequent absences meant that Dumbledore had enlisted Snape's help to cast the spells when he wasn't there. That meant that Snape had a good knowledge of the spells around the school. And if he knew what the protection was, then he could get past it.

Snape wondered whether it would be worth risking everything for this task. If he was caught no one would believe his story, and he would end up in Azkaban. He saw Pettigrew looking up at him expectantly. He realised that he had probably made a mistake when he thought he could trust his former bully, for the simple reason that Peter followed people. He didn't think for himself and would never rise up against anyone, because that would mean he had to rely on himself. Even when he seemed to have betrayed his friends, he was running to Voldemort. It was clear that if Snape wanted his support he had to gain Pettigrew's trust.

Snape made his decision. He had come this far already, he might as well break into Hogwarts. Raising his wand, he began the spells that would leave Hogwarts temporarily unarmed. It was a complicated charm which involved lots of concentration over a long time. Ten minutes in, Snape had barely made an impact on the defences when he heard a loud pop and saw Bellatrix apparate next to him. His concentration was broken and he turned to her.

"Yes?"

"I thought you'd be here, but you don't have any chance of getting in. Not if those defences were put up by Dumbledore."

"Not any more I don't" Bellatrix looked confused but carried on.

"I have a bit of a problem, Hufflepuff's cup is gone."

"So? Look for it! That's what we're doing for the locket"

"You wouldn't have any idea who took it?"

"Why would I? It almost sounds like you're implying I'm the one who took it!"

"Look, I just still don't trust you! You've spent too much time around Dumbledore! All I'm saying is we should swap places. You weren't so close to Dumbledore when the locket was taken but you could have taken the cup. It won't make a difference to you which horcrux you're looking for and it will put my mind at ease."

Snape was furious at her suggestion. He hated her being in charge of this mission and thinking that he was only there to do her bidding. However, he knew better than to let his emotions show on his face. Besides, he knew where the cup was after all, and it would look good for him if he could return quickly while Bellatrix, their leader, was still searching fruitlessly for the horcrux.

"Of course. Your trust is so important to me" Snape didn't realise that next to him, Peter had picked up on the hint of sarcasm in his voice as the two carried on the conversation. Peter began to wonder about Snape. He began to recall his behaviour, how he had seemed on edge and jumpy ever since they had began the task. He was also remembering Snape's strange attitude towards Peter himself. After years of them working together hating each other, Snape seemed, well, civil, which made a change. Peter could only think it had something to do with the secret Snape knew about him, and if it did, well, that couldn't be good. Peter felt a sense of foreboding. Whatever happened next, he was going to have to be on his guard.

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	6. Chapter Five

"Why don't you work on getting into Hogwarts while I go and look somewhere else?" Snape casually suggested to Peter after Bellatrix had left them.

"Where?"

"It doesn't matter, it's just a hunch I have." Before waiting for an answer he left Peter standing alone to try and find his way into the castle.

Peter sighed. He had been counting on Snape to get into the castle, even if then he could run around undetected as a rat. He thought that it must be worth a try just walking up to the school, after all if someone realised there was an intruder they would never look for a rat, especially now that Harry and his friends were looking for the horcruxes and Dumbledore had been killed.

From the castle, a group of figures had watched two people appear at the gates. They had then seen another person arrive and then leave, quickly followed by the taller of the original two. They had also seen the remaining figure turn into a rat and where now watching its progress up to the school. They were ready for a fight.

Peter scurried up to Hogwarts, surprised at the lack of opposition. Growing more bold, he found a small gap in between the door and the ground that he had used to get in and out of the castle when he had been Ron's pet Scabbers. Once inside the great hall, he found a hiding place under a table and began to plan where to look for the cup.

Around the two entrances to the great hall, groups of people began to assemble.

He could check McGonagalls office, but if she was in there she would recognise him… Perhaps there was a trophy cabinet somewhere-or the Hufflepuff common room! That would be the most likely place. He made his way towards the common room.

The group of people waiting by the door tensed as the marauders map Harry had lent them showed Pettigrew moving towards them. He reached the door, and they knew he must be standing on the other side, oblivious to the assembled team of Order members waiting for him.

Peter pushed the door open. As he did he was hit by five stunning spells. He was unable to move as he was picked up and carried up the stairs towards McGonagalls office.

"The Order have caught Pettigrew, Snape."

"What! All he had to do was sneak around the school as a rat, it wasn't hard! How did it happen?"

"Lupin was at the meeting where Voldemort gave out the tasks. He warned the Order and they're guarding the places they think you might look, including Hogwarts. You can't really blame Peter-if you'd got into the school they would have probably caught you as well."

"Well, thanks for the tip off anyway. I'll take the cup to Voldemort, and then I'll see if I can do something to help."

"You think you're going to tell them?"

"I had to some time, and I might as well tell them now and save Peter than later and leave him to a cell in Azkaban, or worse"

"The problem will be persuading the rest of the Order. I have a feeling I might still be the only one who believes you"

Taking Hufflepuff's cup, Snape said goodbye to his informant and apparated to where Voldemort was waiting for him.

"You have it?"

"Here" Snape handed over the cup."

"Well done. I have another task for you. Potter has come too close to greatly weakening me, and I think it's time that I focused all my efforts on attacking him and the Order. This Saturday the order will be at Hogwarts to help with the defences. I'm going to get a team of Death Eaters together to attack them" Snape was shocked. This attack had come a lot sooner than anyone had expected. If he didn't want Voldemort of gain total control, he had to warn the Order what was happening. Telling them wouldn't be hard, but he needed them to believe his story, and for that he needed Pettigrew.

Hundreds of miles away, the few Dementors that were still under the ministry's control were called to Hogwarts to perform the Dementors Kiss on Pettigrew, the man who had returned Voldemort to his former glory, and was, unknown to the Order, one of the only people who could help save their lives.

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	7. Chapter Six

Various members of the Order of the Phoenix were assembled in the Headmistress' office at Hogwarts. They had turned Peter back into a man and he was currently tied up on one of the chairs, being interrogated. The veritaserum had already been used up, and Peter was sitting in stony silence.

"Look, Wormtail. The dementors are on their way, if you tell us something maybe they won't perform the kiss!" Lupin appealed to one of his former best friends. Peter just glared at him. They were suddenly interrupted by a knock on the door and Rufus Scrimgeor entered the room, without waiting to be invited in.

"The dementors are here. Do you want me to bring them up."

"Yes, I think that would be bes-" McGonagall was interrupted by Harry.

"No."

"What?" The minister looked taken aback.

"Dumbledore said that dementors would never enter the castle itself and I think we should stick to his word."

"Oh very well!" Scrimgeor sighed. "Bring Pettigrew downstairs. Honestly" He muttered to himself "No, dementors in the castle… Even Dumbledore allowed them for Black…" He stopped at the glare Harry gave him at the mention of his godfather. "Bring Pettigrew down then!"

Peter, who had been trying to remain calm, couldn't cope any more. "No!" He screamed "No please! Harry… Remus! Remus, how can you let them do this to me! We were friends, I trusted you! Doesn't that count for anything?" He pleaded desperately.

Remus was about to reply when he was interrupted by Harry. "Trust? My parents trusted you! They put their lives in your hands and now their dead!"

"No! Harry you don't understand! I didn't know!" His voice dropped to a whisper. "I didn't know" he sobbed.

Snape was running up the path to Hogwarts when he felt a burning on his arm. "Not now!" he sighed under his breath. He didn't know what to do- he had to warn the order before Peter was soulless, but he didn't want Voldemort to know that there was a traitor in his ranks. He made his decision.

Peter felt himself being dragged down a staircase, his hands still tied. He didn't care what happened to him any more. He had finally let the guilt he had been working for sixteen years to forget engulf him. They left the school and came out into the cold night. The two people who had been steering Peter dropped him and he sank to his knees. Out of the corner of his eye he saw Harry, so similar to James, and Remus, standing together, their faces unreadable. He heard voices but couldn't make out the words. Through blurry eyes he saw a tall black figure moving towards him, felt what little warmth there was leave him. Suddenly, he wasn't outside Hogwarts any more but in a small house in Godrics Hollow.

"_You know why!"_

"_So why don't you just hand us over to him! You're pathetic, you know that? Pathetic!" _

"_I would never do that to you!"_

"_It's not even her he's after! Just leave! I can't stand you!" _

The scene changed suddenly and he was standing in a dark grimy room.

"_Who are you?"_

"_I am the Potters secret keeper"_

"_What?"_

"_I know where they are…just don't kill her!"_

"_Fine, where are they! Tell me!"_

"_Godrics Hollow…" _

"Expecto Patronum!" Peter was suddenly jerked from his past into the present. Some of the warmth and light flooded back. He looked up and saw Snape standing there, with the rest of the Order pointing their wands at him.

"Snape!" Harry hissed. He raised his wand and was about to mutter the incantation when Snape yelled "Wait!"

"Scared now are you?"

"Of you Potter? Never. But I need to tell you something. We're not working for Voldemort. You're making a mistake. Voldemort's coming to attack the school on Saturday!"

"And why should we believe you? You killed Dumbledore!"

"I can explain. And Pettigrew can tell you why he betrayed your parents!"

Glaring at him, Harry answered "Fine then. What's the explanation?"

"Pettigrew…?" Snape implored.

"No! I'm not going to tell them. I'd rather go to the dementors than have Lily's son know what I did!"

"And if you don't they'll never believe me! Lily's son will die because of you! What would she say if she knew what you were doing?"

"I don't even know if you're working for him."

"I can explain all that. Please, just tell them!"

Looking round at all the order, Peter met Harry's questioning eyes.

"OK, I'll tell you. Just remember… I've regretted this everyday since it happened." And with that, Peter began to tell them the story that had haunted him for sixteen years.

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